Cork Oak Wood Research Articles

Lack of Small-Scale Changes in Breeding Birds after a Fire: Does the Resilience of Cork Oaks Favor Rapid Recolonization in Suburban Wood Patches?

Forest fires are disturbance events that can impact biological assemblages at multiple scales. In this study, the structures of breeding bird communities in cork oak patches located in an agro-mosaic suburban landscape of central Italy (Rome) were compared at the local scale with a fine-grained mapping method before (2018) and after (2023) a fire event occurred in July 2022. The analyses did not reveal any significant changes in the density of territorial pairs or in the diversity metrics, both univariate (Shannon–Wiener index, evenness, Margalef normalized richness) and bivariate (Whittaker and k-dominance plots, abundance/biomass curves) of diversity. Even when the guilds of strictly forest-related species were compared, no differences emerged before and after the fire. This counterintuitive phenomenon may be due to the characteristics of the dominant tree, the cork oak (Quercus suber), a sclerophilous tree that is very resilient to fires and able to recover foliage in the following spring season, thus allowing rapid bird recolonization. However, other small-scale phenomena (e.g., the ‘crowding effect’ and local dispersal of territorial pairs from remnant wood patches not affected by fire) may explain this lack of change in breeding bird density and diversity. Further studies should be carried out at larger spatial and temporal scales and at different levels of fire frequency and intensity to confirm these responses at the guild/community level in suburban cork oak wood patches.

Cartographie des déterminants de l’invasion par le pin maritime, Pinus pinaster Ait., de la subéraie de Haddada dans le nord-est de l’Algérie

Plusieurs subéraies du Nord-Est algérien sont sujettes à une invasion par le pin maritime. Cette dynamique forestière qui a débuté dans les années 1980 est souvent citée parmi les facteurs de dégradation des subéraies algériennes mais n’a encore jamais fait l’objet de recherche. L’objectif de notre étude, qui porte sur le cas de la subéraie de Haddada (wilaya d’El-Tarf), était d’identifier les déterminants de l’invasion par le pin maritime, Pinus pinaster Ait., en recourant à une cartographie chorologique de facteurs tels que la pente, l’exposition et les surfaces incendiées en 1994, ainsi qu’une cartographie de la subéraie avant et après l’invasion. L’élaboration des cartes a suivi une approche géomatique complétée par des enquêtes sur le terrain. La cartographie montre que les parties envahies par le pin maritime sont celles qui ont été le plus touchées par l’incendie de 1994, ce qui correspond aussi aux pentes fortes et très fortes. La faible résilience du chêne-liège, Quercus suber, dans ces conditions a permis au pin maritime de le supplanter. Cette dynamique illustre bien le paradigme patch dynamics dans une forêt méditerranéenne, et nous renseigne aussi sur le potentiel invasif du pin maritime, s’agissant d’une espèce se révélant également invasive ailleurs dans le monde. Le changement climatique risque d’accentuer ces processus d’invasion.

Patchy landscapes support more plant diversity and ecosystem services than wood grasslands in Mediterranean silvopastoral agroforestry systems

Plant diversity and proxy indicators of ecosystem services were assessed for three structural components of Mediterranean silvopastoral agroforestry systems: WL = cork oak woodlands, WG = cork oak wood grasslands, and OG = open grasslands. Our study was conducted in a long-term observatory located in NE Sardinia, characterized by fragmented land ownership and land use, which generates a patchy landscape that is different from the extensively studied large scale Iberian dehesas and montados. Our research question was focused on assessing whether, a “patchy” land use scenario made of the combination of WL, WG and OG or a “specialized” scenario could provide more plant diversity and ecosystem services than a “dehesa type” scenario including only WG under the same overall tree cover. The results showed that γ and β diversity, species unique to a position, C stock, cork and acorn production, Hemicryptophytes cover, nectariferous species cover, decreased and pastoral value, excellent and good forage species and legume cover, increased along the WL➔WG➔OG land use gradient. Isolated trees in WG and clearings in WL highly contributed to achieving mainly high C stock and plant diversity respectively. The results also showed that the “specialized” scenario can support higher biodiversity and better ecosystem services than the “dehesa type” scenario, but the “patchy” scenario made of all three components proved to support the highest level of both biodiversity and ecosystem services in Mediterranean silvopastoral agroforestry systems.

Impact des perturbations anthropiques sur la diversité végétale de la subéraie de Chréa, au nord de l’Algérie

La subéraie de la réserve de biosphèrede Chréa, au nord de l’Algérie, révèle une action anthropique ayant profondément modifié le paysage végétal. Les feux récurrents et le surpâturage sont les principales perturbations des formations forestières présentes, s’agissant de perte de surface et de biomasse végétale. Notre objectif était de savoir comment, au sein de cette réserve, réagit la végétation de l’écosystème à Quercus suber L. aux conditions de milieu et aux perturbations liées à l’activité humaine. Pour y répondre, nous avons adopté une approche synchronique en réalisant 124 relevés phytoécologiques dans les différents stades dynamiques, en tenant compte de la présence ou de l’absence de la perturbation liée au pâturage. Une première analyse canonique des correspondances a porté sur les données floristiques et les variables environnementales ; une seconde concernait les attributs vitaux des espèces, en utilisant les traits de vie facilement mesurables (type biologique, stratégie adaptative de Grime, mode de dissémination). Les résultats montrent que la végétation de la subéraie s’organise le long d’un gradient de dégradation lié à l’action anthropique (incendies et pâturage), masquant l’effet des facteurs mésologiques dominants (altitude et exposition). L’approche fonctionnelle confirme cette dynamique régressive avec l’individualisation de deux groupes fonctionnels. Le premier recouvre les traits de vie « phanérophyte, compétition-stress, zoochore », caractéristiques des formations végétales les plus matures. Le second groupe englobe les traits « thérophyte, stress-rudéral, anémochore », liés aux formations ouvertes des pelouses surpâturées. Cette étude, conduite selon une approche fonctionnelle de la biodiversité, est une première évaluation de la réponse des subéraies algériennes aux perturbations anthropiques représentées par les incendies et le pâturage.

Hydrodeoxygenation of Pyrolysis Bio-Oil Over Ni Impregnated Mesoporous Materials.

The catalytic hydrodeoxygenation (HDO) of bio-oil over Ni-supported mesoporous materials was performed using a high pressure autoclave reactor. The actual pyrolysis oil of cork oak wood was used as a sample, and Ni/Al-SBA-15 and Ni/Al-MSU-F were used as catalysts. In addition, supercritical ethanol was added as solvent. Both Ni-supported mesoporous catalysts showed efficient HDO reaction ability. A higher heating value and pH of bio-oil were achieved by the HDO reaction over both catalysts and upgraded bio-oil had a lower viscosity. Compared to Ni/Al-MSU-F, Ni/Al- SBA-15 produced more upgraded bio-oil with a lower oxygen content and higher heating value via a catalytic HDO process.

Airborne propagules of Phytophthora and related taxa in SW Spain including a predictive model

The airborne sporangia of Oomycota, including Phytophthora species and other species, are usually recorded by volumetric spore traps. The aim of this work was to create a predictive model for the seasonality and weather parameters that may affect sporangia distribution by analysing their presence over the course of a year. Three Hirst spore traps were located in the SW of Spain (Plasencia, Don Benito and Zafra), and the presence of sporangia was recorded throughout 2012–2013. Phytophthora sporangia were recorded on 76–110 days per year. Autumn and spring were the seasons when the highest concentration peaks of airborne sporangia were recorded; these peaks were recorded on the same day in each of the three locations. When analysing weekly sums of the daily concentration of sporangia, there was a statistically significant correlation between the sporangia concentration and amount of rain in the three locations studied; however, this correlation was not observed when comparing the individual daily concentrations. When comparing the daily concentration to the daily rain levels, the highest correlation coefficient and statistically significant correlation was reached on the second day after rain. The proposed predictive model considered the previous rain to be the main environmental factor. Holm oak and cork oak woods in Plasencia may be responsible for a higher concentration of airborne Phytophthora-type sporangia. Rain seems to have a direct influence on the concentration of airborne sporangia, but the highest concentrations appear on the second day after rain.

Cork oak (Quercus suber L.) wood hygroscopic properties and dimensional stability

Cork oak (Quercus suber L.) wood has a potential for high value uses because of its strength and aesthetic properties but one obstacle is the lack of knowledge of the wood-water relations. Variations in wood equilibrium moisture content, density and dimensions were studied at air temperatures of 22°C and 27°C (representing acclimatized homes and summer non-acclimatized homes, respectively) varying from 80% to 30% of relative humidity. For indoor uses (22-27°C, 50-65% of relative humidity), the wood equilibrium moisture content ranged 12-17% and these values are recommended for the final commercial drying of cork oak wood. The fibre saturation point averaged 27%. Total volumetric shrinkage at 22°C-27°C averaged 12%, the linear shrinkage 8.1-8.5% and 3.6-3.6%, respectively in tangential and radial directions. Anisotropy averaged 2.3. Wood density at 12% moisture content ranged 0.63 to 0.67 g/cm3. The higroscopicity obtained was 0.003. The average tangential differential shrinkage was 0.32 for both temperatures and the average radial differential shrinkage was 0.14 and 0.15, at 22°C and 27°C respectively. The shrinkage factor was 0.90 cm3/g and 0.82 cm3/g, at 22°C and 27°C respectively. Differences between temperatures were only statistically significant at 80-70% of relative humidity.

Properties of cork oak wood related to solid wood flooring performance

Application of cork oak wood as solid wood elements for flooring was experimentally assessed by measuring dimensional stability to air humidity and liquid water, response to loads applied while in service and abrasion due to people traffic using boards cut from the stem of five mature cork oak trees (Quercus suber L.). The results obtained from dimensional stability tests showed a performance of a medium movement in-service and small swelling in liquid water (2–3%). Hardness (55N/mm2) and wear resistance allowed classifying cork oak wood as suitable for all domestic (including heavy traffic) and moderate commercial end-uses.

Effects of Mediterranean summer conditions on chlorophyll a fluorescence emission in the epiphytic lichen Flavoparmelia soredians: a field study

Recent hypotheses suppose that dry lichens emit a faint chlorophyll a fluorescence because of a “long-wavelength quencher” embedded in the antenna complex that protects photosystem II (PSII) from photodamage. To verify in the field the PSII re-activation promptness induced by water availability, chlorophyll a fluorescence was measured on the epiphytic lichen Flavoparmelia soredians after two months without rainfall events in a Mediterranean cork oak wood (Bosco Santo Pietro, Sicily, Italy). Measurements were carried out at dawn and sunset on north- and south-exposed populations under different regimes of hydration and dark-adaptation. The results show that prolonged hydration increases the photochemical conveying of energy to PSII and decreases the non-photochemical energy dissipation that otherwise might occur in the antenna complex of the lichen photobionts. A slight decrease in PSII efficiency caused by photoinhibition was observed in thalli exposed to ambient light (up to 600 μmol photons m−2 s–1) only when kept fully hydrated. The results are discussed on the basis of our knowledge on the ecology of the species, that is a representative component of Mediterranean epiphytic lichen communities.

Kinetic and diffusive data from batch combustion of wood chars in fluidized bed

In this work it is studied the combustion of batches of wood char particles in a shallow fluidized bed at laboratory scale. Commercial and recarbonized chars from nut pine and cork oak parent woods were burned for bed temperatures of 600–750 °C and particle sizes range of 1.8–3.6 mm. A combustion model based on the two-phase theory of fluidization is presented to evaluate the global combustion resistance. Sherwood numbers and kinetic constants for the heterogeneous phase reaction are also assessed. Through the comparison among theoretical and experimental results, conclusions are drawn on the combustion mechanism as well as on the combustion controlling resistance. The Arrhenius law is proposed to predict the kinetic constants for the studied chars. ► Combustion of nut pine and cork oak wood char particles was studied in a laboratory shallow fluidized bed. ► Covered temperature range from 600 to 750 °C and covered particle size range from 1.8 to 3.6 mm were used. ► Commercially carbonized and recarbonized chars were tested and an Arrhenius law is proposed for these chars.

Stem modeling and simulation of conversion of cork oak stems for quality wood products

Recent research is underway to study cork oak (Quercus suber L.) wood potential for production of wood components. A total of 35 stems of young and mature cork oaks were sampled, live sawn into flitches, scanned using VTT’s WoodCIM®, and the measured data computed by VTT’s PuuPilot software, allowing stem 3D reconstruction. Sawing simulations were run for 0.5 m and 1 m logs and the whole stem. Sawn products were (1) planks, (2) parquet, (3) lamparquet, and (4) external component of multilayer planks. Cork oak stems showed a moderate to small taper (mean 24 mm/m). Curviness varied between straight to significantly crooked stems (mean value 40 mm) Batch yields for the tested products ranged 25–43% and 37–50% for 0.5 m logs of young and mature trees, respectively; for 1 m logs, batch yields ranged 19–41% and 25–54%. When using the whole stem, batch yields were lower, ranging 11–38% and 15–50%. Higher yields were obtained for all log lengths and samples for production of lamparquet, parquet, and multilayer component.

Differences of raw cork quality in productive cork oak woods in Sicily in relation to stand density

Differences of raw cork quality, in terms of thickness and porosity, were observed in productive cork oak ( Quercus suber L.) stands in the Nebrodi and Iblei mountains of Sicily in relation to stand density. Five study areas were chosen across a range of different stand density satisfying specific sampling requirements among two managed cork oak woods.Analysis of variance using Fisher–Snedecor‘s F test ( p < 0.05) were used to identify statistically significant differences of cork quality and sylvicultural, dendrometric and cork stripping parameters between study areas within each stand. Relationships between cork quality and sylvicultural and dendrometric parameters were also tested using Pearson's correlation coefficient ( r). Results shown that sylvicultural practices are a key factor influencing cork quality: statistically significant differences in cork thickness and crown area were observed between areas at different stand density; positive correlations were found between cork thickness and crown area in lower density study areas favouring a significant vegetative activity; negative correlations were found between parameters of cork stripping (cork stripping coefficient, cork stripping surface, maximum height of cork stripping) and cork thickness. No correlations were found between cork porosity and dendrometric or sylvicultural parameters, demonstrating the probable genetic origin of cork porosity. Results shown that cork quality parameters and stand attributes may be used in sustainable management models of cork oak forests.

Characterization of Cork Oak (Quercus Suber) Wood Anatomy

The cork oak (Quercus suber L.) is important for ecological and socioeconomic sustainability and nature conservation in the Mediterranean area. Anatomical and structural features of cork oak wood were characterized at two sites in Portugal, including never-debarked trees and trees under cork production. Cork oak wood showed semi-ring porosity, solitary vessels with simple perforation plates, and large rays. Vessels were arranged in a diagonal to radial pattern, larger and more abundant in earlywood, and gradually decreasing in intermediate and latewood. In trees under cork production vessel distribution and frequency were altered, with more frequent and smaller pores, and a less distinct porosity pattern. Vessel diameter, element length and frequency were 133 ± 49 μm, 433 ± 103 μm and 2.9 ± 0.5 vessels/mm2 for never-debarked trees and 139 ± 50 μm, 341 ± 100 μm and 5.1 ± 1.5 vessels/mm2 for debarked trees. Multiseriate ray width ranged 0.15–1.04 mm, and uniseriate ray height 9.1–791.3 μm. Fibres had a mean length of 1.15 ± 0.20 mm. Vasicentric tracheids were frequent. Tyloses and crystals were commonly present. The anatomical features of cork oak wood favour water conduction and mechanisms of drought adaptation to the Mediterranean climate. The wood can also adapt to cork removal.

Within-tree and between-tree variation of wood density components in cork oak trees in two sites in Portugal

Summary The axial and radial variation of wood density was studied using microdensitometry in cork oaks ( Quercus suber ) in two sites in Portugal. The observations were made in mature trees under cork production and in juvenile trees before the fi rst cork extraction, at three height levels (stem base, 1.3 m and before stem bifurcation). The cork oak wood revealed a very high mean density (0.884 – 1.068 g cm 3 ). Differences between earlywood and latewood were small (0.866 and 1.061 g cm 3 , respectively). Latewood corresponded on average to 61 per cent of the total. The variation of density between trees was statistically highly signifi cant, but no differences were found between the two sites. The within-tree axial variation was negligible but the radial direction within a cross-section was one of the main origins of variation of the density components (18 per cent of the total variation). The density decreased from pith to cambium and this radial variation corresponded to 19 – 24 per cent of the total variation of wood density. Overall, the magnitude of density variations between and within cork oaks was small and an advantageous factor for their use for quality wood products.

Cork oak (Quercus suber L.) wood growth and vessel characteristics variations in relation to climate and cork harvesting

Variations in tree ring growth of Quercus suber L. were analysed using dendrochronological techniques on cork oak discs from trees harvested in the cork producing region of Alentejo, Portugal. A tree-ring chronology containing a strong common signal and covering the period from 1970 to 1995 was build for ca. 30-year-old cork oaks never submitted to cork harvesting using 14 trees that crossdated satisfactorily out of 30 sampled trees. The tree ring indices correlated positively with September temperature (r = 0.48, P < 0.05) and very strongly with precipitation totals from previous October until current February (r = 0.82, P < 0.001) showing that the water stored in the soil during the autumn and winter months prior to the growing season has a primordial effect on the growth of the given season. The effects of cork harvesting were analysed by comparing mean ring width, mean annual vessel area, vessel density (n°vessels/mm2), and vessel coverage (percentage of transverse surface occupied by vessels) between three mature cork oak trees and three young trees, for the period from 1987 to 1996, corresponding to the growth between two consecutive cork removals in the case of mature trees. In 1988, 1989 and 1996 (corresponding to the first and second years after cork removal, and 1996 to a year of cork removal), the ratios between ring widths of young versus mature trees was twice that for the rest of the period. However, an effect of cork removal indicated by eventual alterations in vessel size and distribution in the wood rings corresponding to the years 1988, 1989 and 1996 in the mature cork oaks was not observed.

Radial variation of wood density components and ring width in cork oak trees

The radial variation of ring width and wood density was studied in cork oaks (Quercus suber) using microdensitometry. The observations were made in young never debarked cork oaks (30–40 years of age) and in mature trees under cork production (37–60 years of age). The cork oak wood is very dense (mean ring density 0.86 g.cm−3, between 0.79 g.cm−3 and 0.97 g.cm−3) with a small intra-ring variability (mean earlywood density 0.80 g.cm−3 and latewood density 0.90 g.cm−3). The density components decreased from pith to bark more rapidly until the 15th ring, and then only slightly. There were no significant differences in the mean density components between never debarked trees and trees under cork production but their outwards decrease was accentuated in the never debarked trees. The annual growth was high, with a ring width mean of 3.9 mm (4.2 mm in the first 30 years) and the latewood represented 57% of the annual growth.

Radial variation of vessel size and distribution in cork oak wood (Quercus suber L.)

Quercus suber L. is an important species producing cork whose wood characteristics have not been investigated a lot. Cork oak wood vessels are a striking feature and the most abundant wood tissue largely influencing density and permeability. Vessel size and distribution were studied in approximately 40 year-old and never debarked cork oaks by continuously measuring along the radial direction in the transverse section of wood discs taken at 1.3 m of height using image analysis techniques. The vessel size increases with age from 7660 ± 2286 to 21136 ± 6119 μm2, the conductive area from 5.4 ± 2.2 to 11.6 ± 3.9%, and the vessel density remains approximately constant between 5.2 ± 1.5 and 7.3 ± 3.5 vessels/mm2. In comparison with ring-porous and some evergreen oaks, cork oaks show a similar conductive area but smaller vessels. Vessel architecture is known to play an important role on oaks tolerance to hydric stress, and these cork oak trees were growing under very harsh edaphoclimatic conditions, not tolerated by other oaks. The well-developed and deep root system allowing access to constant water supply may contribute to the cork oak’s relatively high conductive area.

Within and between-tree variation in the biometry of wood rays and fibres in cork oak (Quercus suber_L.)

The variability of fibre and ray dimensions was studied at three radial positions (10, 50 and 90% of radius) in 5 cork oaks (Quercus suber L.) approximately 40 years old. Uniseriate ray height and cell number as well as multiseriate ray height and width were measured in tangential sections. Fibre length, width and wall thickness were measured after maceration. The most striking features of cork oak wood were the large multiseriate rays and the frequent homocellular uniseriate rays. On average multiseriate rays were 5.16 mm high and 0.48 mm wide, and uniseriate rays contained 11 cells and were 227 μm high. Neighbour rays presented large dimensional differences but there was no radial variation and there were very small between-tree differences. The radial maintenance of high and wide rays was discussed as a means to improve water shortage in response to water stress. Fibre dimensions increased radially but differed little between trees: on average, 960–1,220 μm length, 18.40–21.49 μm width and 6.66–8.07 μm wall thickness. The ray pattern showed enough variation for visual appreciation while ensuring within and between-tree uniformity. The presence of rays has to be taken into consideration for designing wood drying programs.

Forest defoliation using IKONOS sensor for cork oak (Quercus suber L.) woods in Southern Spain

Assessment of forest defoliation is severely hampered by the limited information on tree death on short temporal and broad spatial scales. In order to evaluate forest decline rates in cork oak of Southern Spain, an analysis was made of statistical correlation between the 4 IKONOS sensor original bands acquired in 2000, the Normalized Difference Vegetation Index (ndvi) and Infrared/Red Index (ir/r) and defoliation information obtained from the ground study. IKONOS near infrared band was negative correlated with defoliation (Pearson Correlation –0.762). The correlation between defoliation and ir/r ratio (Pearson Correlation –0.506) and ndvi (Pearson Correlation –0.449) was also significantly correlated. The dispersion of data presents in each category of defoliation justifies the use of the median value as the representative variable value for each intervals of defoliation. The Statistical Index of Defoliation (SID), generated from a lineal combination of IKONOS sensor bands, shows a correlation rate of 0.85 with the deforestation ground estimate which allows to estimate defoliation by using the equation: Y% defo calcu = –0.0016 * SID + 1.2162. This study shows that high-spatial-resolution satellite data can now be used to measure forest decline processes, suggesting many new alternatives to evaluate the impact of forest decline in Mediterranean forests.

Three new species of Stibeutes and Gnotus (Hymenoptera: Ichneumonidae) from holm-oak and cork-oak Mediterranean forests

AbstractThe new species Stibeutes hirsutus, S. calderonae and Gnotus klausi from Spanish holm-oak and cork-oak woods are described and illustrated. Data on their habitat and the phenology of S. hirsutus are reported. The species S. breviareolatus collected in a cork-oak forest is recorded for the first time for Spain. New keys for the Gnotus tenuipes species group and for the Spanish species of Stibeutes are provided.